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EQUIPMENT FORUMS >> SE84UFO >> Tube rolling & bios, Ohm load switches
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Message started by Dana on 02/03/22 at 21:25:47

Title: Tube rolling & bios, Ohm load switches
Post by Dana on 02/03/22 at 21:25:47

Been playing with my UFO84 for a while now and am enjoying the heck out of it. I first upgraded the rectifier as the the one that came stock created a little light show when I clicked it on.

I've since been trying to only change one thing at a time but changing one thing affects everything else.

NOS rectifier tube really helped the sound.

With the assistance of the forum gurus was able to rectify a bad purchase due to ebay mislabeling. The EL83 is not the same as a SV83. I could have fixed it with adapters but as they wouldn't cancel my order I received some EL84s instead. I then found some Russian output tubes for cheap and prefer them to the EL84s that I have.

I'm now onto input tubes. I tried several different Russian 6N1P-EV and 6N1P and they weren't the best match for the sound I preferred. I tried some 6922s and different brands presented a completely different presentation and today trying my first 7308 input tube.

Long story (sorry) but I have a question and an observation.

The speaker OHM switches appear to increase the focus but reduce the width and I can move the presentation really forward or widen it with the bios ohm combination.

My question is there a way without voiding the warranty to further adjust the bios? I'm having a Goldilocks issue of to heard to soft.

Cheers,

Title: Re: Tube rolling & bios, Ohm load switches
Post by Dana on 02/04/22 at 04:59:07

The bias (computer guy ... BIOS is not bias) switch that adjusts the tube bias. Similar to the Transformer Ohm switch only more so.

It's probably switching between two values of resistors and I could add some resistance to one leg but I'm sure that would completely void my lifetime warranty.